The present invention relates generally to a flexible connecting device and to a flexible stabilization system with such a flexible connecting device, especially for use in spinal surgery. Furthermore, the invention also relates to a corresponding modular system.
Flexible stabilization devices for the spine are known. US 2003/0109880 A1 discloses a stabilization system with an elastic rod element, which is provided as a connecting element between two bone anchors, whereby the elastic rod element is formed from a helical spring with narrow threads.
WO 2005/030031 A2 and WO 2005/039454 A2 similarly disclose flexible spinal stabilization systems in which different types of flexible connecting rods are provided between bone anchors. These patent documents propose that flexible connecting rods for achieving flexibility or mobility should have spiral cuts or slits and be combined with core rods in order that both, flexibility and rigidity, or together defined as spring properties, may be adjusted correspondingly.
Similar considerations apply to EP 0 677 277 A2, which also describes a dynamic or flexible stabilization device, especially for the spine, in which, again, a rod with cuts or a spiral slit is provided as a flexible connecting device. A viscoelastic material may be filled into the cavity of the part with the slit.
WO 03/047442 A1, in turn, proposes a damping element and a device for stabilizing adjacent vertebral bodies. In a first embodiment, two elastic elements are coaxially arranged one inside the other and are connected to two connecting elements. One elastic element is a spirally slit tube and the other is a core element. In a second embodiment, a tubular spring element with a spiral arrangement of slits has a one-piece connector and a receiving opening for adjacent flexible elements. A second spring element is provided as a core element within the first spring element.
US 2003/0220643 A1 similarly discloses a flexible stabilization device for the spine, whereby, again, spiral-spring-like connecting rods are provided between pedicle screws or bone anchoring elements. US 2003/0220643 A1 additionally proposes providing the spiral-spring-like connecting rods with sleeves which act as spacers between the pedicle screws to prevent too much deformation or mobility.
WO 2004/105577 A2, in turn, describes a spinal stabilization system in which differently shaped, flexible connecting rods are used between the bone anchors. They consist of metal strips wound spirally into tubes or of structures braided from metal fibers. Also described are spring elements which are inserted between rods or spirally slit cylindrical tubes with and without cores.
Although some of the above-described prior art stabilization systems have very good properties, the goal remains to create a flexible connecting device for arrangement between bone and vertebral anchors, that replicates the complex, mechanical properties of the spine. Such a device ideally provides adequate support as well as retention of mobility in damaged spinal regions, and is easy to manufacture and easy to manipulate by the surgeon during surgery.